In recent years, wireless transmission of a high-definition video image signal has attracted attention. This necessitates transmitting of large capacity information, and therefore there have been attempts to develop a wireless video image transmission device using a millimeter-wave capable of securing a wide band. In a millimeter-wave band, when an antenna and a high frequency circuit are separately prepared and are then connected with each other via a connecting member such as a connecter, a large power loss occurs at their connecting section. For the purpose of reducing the power loss at the connecting section, an antenna-integrated module, in which an antenna and a high frequency circuit are included in a single module, has been developed.
An exemplary antenna-integrated module is disclosed in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 237867/1997; published on Sep. 9, 1997). FIG. 7 is a drawing for explaining an arrangement of an antenna-integrated module included in a conventional wireless communication device. As shown in FIG. 7, this antenna-integrated module includes an antenna circuit board A and a high frequency board B which are stacked. The antenna circuit board A includes a first dielectric substrate 902 having an antenna element 903 and high frequency lines 904 and 905 via which electric power is supplied to the antenna element 903. The high frequency board B includes a second dielectric substrate 907 having (i) a cavity 908 in which a high frequency device 909 is contained and which is sealed by a cover 910, and (ii) transmission lines 911 and 912 via which a signal is transmitted to the high frequency device 909.
However, the following problem arises from an antenna-integrated module having the above arrangement. That is, most of high frequency signals generated in a high frequency circuit are radiated via an antenna. Some of the high frequency signals become respective surface wave that propagates over a surface of the antenna circuit board A, and then the respective surface wave is radiated from an end of the antenna circuit board A. When the size of the antenna-integrated module is decreased, the surface wave radiated from the end of the board greatly affects the antenna-integrated module, so that efficiency of the antenna is deteriorated.